怎么使第五个数据更加精确？

Question

Answer 1

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]) 
{
    int i,j=1,n;
    double p,sum = 1;
    scanf("%d",&n);
    for(i = 1;i <= n;i++)
    {
        j=j*i;
        p=1.0/j;
        sum = sum + p;
    }
    printf("%.10lf",sum);
    return 0;
}